Purpose: To create a quantitative microbial risk assessment (QMRA) model to rapidly generate risk estimates for invasive listeriosis in susceptible Canadian subpopulations given contamination of RTE meats with L. monocytogenes.
Methods: A QMRA model using Monte Carlo simulation was developed with the Microsoft Excel add-on, @Risk 5.5. National and provincial prevalence data for immunocompromised subpopulations were gathered. A sub-model was created to simulate the overall prevalence of general and susceptible subpopulations, accounting for random overlapping of conditions. Relative risks to susceptible subpopulations were determined by adjustment of the general population dose-response model with relative susceptibility factors. Test simulations were run using default model parameters to simulate a hypothetical contamination event.
Results: The proportion of illnesses attributed to each subpopulation indicated that individuals with liver disease (28%) and cancer (24%), followed by alcoholics (11%) and the elderly (7%), were most at risk. However, cases of listeriosis are infrequently reported in the liver disease and alcoholic subpopulations, which may indicate misdiagnoses or lack of dietary exposure to such foods.
Significance: The QMRA was designed to be a rapid risk assessment tool with the ability to predict the number of cases of listeriosis that may occur following a contamination event when combined with information on the population that may be exposed to a RTE meat product. The QMRA can be used to identify key subpopulations for targeted messaging efforts in the event of a real or suspected L. monocytogenes contamination event.